The invention relates more particularly to sensors comprising a sensing cell in the form of a plate having defined therein a portion forming a support member and at least one vibrating element associated with excitation means. The excitation means enable the vibrating element to be set into vibration and enable the frequency of vibration thereof to be detected.
In an accelerometer, the inertial element is connected to the vibrating element. In most cases, the inertial element is a mass, which is itself defined in the plate and movable relative to the support member. When the sensor is subjected to an acceleration, the mass exerts a force on the vibrating element. This force modifies the frequency of vibration in such a manner that the variation in the frequency of vibration of the vibrating element enables the acceleration to which the sensor is subjected to be determined.
In order to avoid mechanical coupling between the vibrating element and the support member, it is general practice to provide an intermediate frame. Such mechanical isolation also lengthens the heat transfer path. This presents the advantage of ensuring that the temperature of the vibrating element is more uniform, thereby decreasing stresses of thermal origin and the associated parasitic effects. In spite of such arrangements, it has been found that variation in the frequency of vibration of the vibrating element continues to occur independently of variation in the acceleration to which the sensor is subjected, thus giving rise to parasitic variations in frequency interfering with the measurement of acceleration. So long as such parasitic variations exist they reduce the accuracy with which acceleration is measured.